One of the charitable objects of Charcot-Marie-Tooth UK is “the promotion of research into the causes and treatment of CMT/HMSN/PMA and the publication of the useful results of such research”
There has been much progress in the identification of the causes of CMT, that is the genes that cause the problem.
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The first causative gene for CMT was identified in 1991 and to date more than 100 causative genes have been identified for CMT. Recent studies have found that about 75% of patients with CMT get an accurate genetic diagnosis after attending specialised clinics. This represents a dramatic change over the last two decades and reflects the increasing number of new genes being identified.
At the same time it is very frustrating for patients that the development of therapies has not been as successful.
One of the main challenges in developing therapies for CMT is the number of causative genes identified. CMT1A is the commonest form of CMT in the UK accounting for about 60% of patients. CMTX1) is the second commonest cause accounting for about 10% of cases.
The remaining 76 genes affect the other 30% of the CMT population and there are more genes yet to be identified. This means that other than the 2 common genes, the other forms of CMT are very rare with many affecting just a few families and in some cases just a single family.
The second major challenge in developing treatments for CMT is that fortunately CMT (especially CMT1A) is a very slowly progressive disease that does not usually affect life expectancy. This means that any treatments developed have to be very safe especially as most forms of CMT start in childhood.
One treatment approach is “anti sense treatment” which aims to fool the cell into better behaviour – in this case by into producing a normal or near normal protein. There are problems in understanding the risks of such treatments – delivery of the treatment may be by a virus, for example. The delivery of treatments is a problem – the blood / nerve barrier is difficult to penetrate to get drugs from the blood into the nerve cells. And the treatments will probably differ for the more than one hundred causative genes identified to date.
Another approach is pathogenesis – targeting what the gene does. For example an extra copy of one causative gene causes too much of a particular protein to be produced. Treatments would reduce the amount of that protein. Treatments are still being sought – and again the large number of causative genes magnifies the problem.
At the next level, treatments to repair damaged nerves are being sought.
It is important to acknowledge that there are treatments for many of the complications of CMT and therefore although there are no disease specific treatments to either halt the progression or cure CMT, the condition can be managed in most patients. Current treatments include physiotherapy, orthotics, occupational therapy, pain and fatigue management and when indicated orthopaedic surgery, speech therapy and respiratory support to name a few.
We hope that this page has highlighted the challenges in developing treatments for CMT. While Charcot-Marie-Tooth UK would wish to address them, we have to recognise the difficulties in meeting these challenges, given the scale of our resources. We are tending to shift our strategy towards supporting feasibility studies to get such bigger projects off the ground, and to look to small steps to help manage CMT, both its physical issues and now also its effect on mental health.